Image forming apparatuses are equipped with an input device for selecting various functions and inputting numeric numbers. As such input devices, there are one with hard keys to be subjected to press actions, one which includes a display section and a touch panel overlaid on a screen of the display section and in which soft keys are displayed on the screen of the display section and touch gestures on the soft keys are detected through the touch panel, and one in which hard keys and soft keys are used in combination.
For example, in Patent Literature 1, numeric keys are displayed as soft keys on a screen of a display section and a touch gesture on any numeric key is detected through a touch panel. In Patent Literature 2, a hard key or a soft key is used.
In Patent Literature 3, both hard keys and soft keys are used. Furthermore, an individual number is previously associated with one of functions and, upon input of a number by an action on one of numeric keys (hard keys), the function associated with this number is selected. In this case, the numeric keys are used not only for inputting the numeric numbers but also for selecting the functions.
Meanwhile, if, in the case of using soft keys, an error occurs in the coordinate positions of touch gestures thereon detected through a touch panel, a touch gesture on such a soft key on a screen of a display section is not determined to be a touch gesture on this soft key and may cause a malfunction. Therefore, generally, simulation processing for correcting the coordinate positions of touch gestures to be detected through the touch panel is performed.
For example, in Patent Literature 4, numeric keys are displayed as soft keys on a screen of a display section and the coordinate positions of touch gestures are stored upon input of a passcode by actions on some of the numeric keys. When the passcode is correct, comparison is made between the coordinate positions of the touch gestures and the display positions of the numeric keys and the coordinate positions of the touch gestures are corrected. In this manner, each time the passcode is input, the coordinate positions of the touch gestures are automatically corrected.